Combination drafting instrument



Jan. 29, 1946.

G. "H. THuRs'roNi COMBINATION DRAFTING INSTRUMENT Filed March 9, 1944 2 Sheets-Sheet 1 Jan; 29, 1946. Q H, THURSTN 2,393,873

COMBINATION DRAFTING INSTRUMENT File'd March 9, 1944 2 sneets-sheet. 2

Patented Jan. 29,` 1946 UNITED STATES PATENT OFFICE 2,393,873 COMBINATION DRAFTIN G INSTRUMENT George H. Thurston, Camp Hood, Tex. Application March 9, 1944, Serial No.. 525,715

1 Claim.

The present invention relates to new and useful improvements in drafting instruments, and has for its primary object to provide, in a manner as hereinaftei` set forth, a device of this character comprising a T-square, triangle and revolving protractor, whereby all portions of mechanical drawings, with the exception of circles, may be rapidly and accurately made.

Another very important object of the invention is to provide a unique construction and arrangement for mounting thev rotary protractor and the T-square blade on the instrument.

Other objects of the invention are to provide a combination drafting instrument of the aforementioned character which will be relatively simple in construction, durable, compact and which may be manufactured at low cost.

All of the foregoing, and still further objects and advantages of the present invention, will become apparent from a study of the following specication, taken in connection with the accompanying drawings wherein like characters of reference designate corresponding parts throughout the several views, and wherein:

Figure 1 is a top plan view of a drafting instrument constructed in accordance with the present invention.

Figure 2 is a view in side elevation of the device.

Figure 3 is a View in vertical section through an intermediate portion of the instrument.

Figure 4 is a plan view of the lower lamination of the base or triangle. l

Figure.5 is a top plan view of the upper lamination of the triangle.

Figure 6 is a detail View in plan of the lower disc of the rotary protractor.

Figure 7 is a plan view of the upper disc of the rotary protractor.

Figure 8 is a plan View of the rotary square blade.

Referring now to the drawings in detail, it will be seen that the embodiment of the invention which has been illustrated comprises a 45 triangle which is designated generally by reference character I. The triangle I includes upper and lower laminations 2 and 3, respectively, of suitable transparent material, preferably Celluloid, which laminations are adhesively secured together. Scales 4 are provided'on the marginal portions of the upper lamination 2 of the triangle I The laminations 2 and 3 of the triangle I have formed centrally therein registering circular openings and 8, respectively. As illustrated to advantage in Figure 3 of the drawings, the opening 8 is of slightly larger diameter than the opening 5. The triangle I is further provided with a multiplicity of circular holes 'I of various sizes.

The openings 5 and 6 in the laminations 2 novel combination of square,

imposed laminations secured a unit of geometric dimensional projections and and 3 accommodate a rotary protractor which is designated generally by reference character 8.

The protractor 8 comprises upper and lower discs 9 and I0, respectively, which are adhesively secured together. The discs 9 and I 0 are also of suitable transparent material, such as Celluloid. It will be observed that the lower disc I 0, which is operable in the lower opening 6 of the triangle I, is of slightly larger diameter than the upper disc 9. The marginal portion ofthe upper disc 9 of the protractor 8 is provided with a scale II Adhesively secured on the upper disc 9 of the protractor 8 for rotation therewith is a substantially oblong lanceolate blade I2 of Celluloid or other suitable transparent material. The base portion I3 of the blade I2 is coaxial with the protractor 8 and is slightly larger than the disc 9. Thus, the marginal portion of the base portion I3 of the blade I2 projects over the upper lamination 2 of the triangle I. In this manner the elements I3 and I0 coact for rotatably securing the protractor 8 and the Iblade I2 on the triangle I. This is also shown to advantage in Figure 3 of the drawings.

The portionA I3 of the blade I2 and the discs 8 and I0 of the rotary protractor 8 have formed therein registering radial slots I4. Outwardly of the slots I4 therein, the blade I2 is further provided with a longitudinal slot I5. The upper disc r9 of the rotary protractor 8 is further pro-v vided with spaced, concentric circles I 6 which the slots I4 intersect.

It is believed that the many advantages of a combination drafting instrument constructed in accordance with the present invention will be readily understood, and although a preferred embodiment of the device is as illustrated and described, it is to be understood that changes in the details of construction may be resorted to which will fall within the scope of the invention as claimed.

What is claimed is:

A device of the character in combination, a triangle described comprising, consisting of supertogether to produce having various geometric indicia thereon, a rota.- tively actionable protractor disposed on said triangle including superimposed discsy rotatable in Y relatively corresponding reception recesses in said triangle, and an instrument of oblong lanceolate contour having its base fixed coaxially on the upper disc of said protractor, the marginal portions of said instrument converging to a point extending beyondthe marginal edgesof said triangle, said instrument being transparent to permit of the reading therethrough of the graduations and projecting indicia on said triangle and protractor.

GEORGE H. THURSTON. 

